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Tank MPG Calculator Off

3504 Views 6 Replies 7 Participants Last post by  bunker108
Don't know if you guys ever calculate on your own your MPG per tank but I noticed the dash mpg read out is consistently 0.4 mpg too low (e.g., Dash says 15.6 mpg and actual is 16 mpg).

I picked up an 08 IS F with 21K miles on it 3 weeks ago and been averaging about 15-16 MPG per tank around town. That is if I really don't kick it above 4,000 RPMs. If I really dog it, I'm averaging around 13-14 MPG. Does that seem low to you all?
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I average 16 to 17 according to the car and I'm on it all the time. I don't drive the car much so when I do its hard.
Wow, i get like 12-13 max per tank. I guess i must drive pretty hard...
Yes, I have noticed that the MPG calculator is off. Since I don't have far to drive to work, and I travel overseas a lot, I let my wife drive the ISF to work 4 days a week...mostly highway driving (70+ miles round trip to work).

I drive the ISF hard in short bursts only, so the tank average usually doesn't suffer too bad. The tank average indicator usually says around 19 MPG. Every time I calculate the actual tank average when filling up, it is right about 20 for me, it has been off by about 1 MPG.
I drive mine so it shifts around 3-4k rpm with and occasional full throttle bursts and I average 20mpg, every time I've calculated it myself its matched what the car said.
That sounds about right. Mine is usually within .4.
.4 low is right on...this morning when I filled up the dash told me 18.6, but by hand it was 19mpg.
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